It is often desirable to provide visual information to a living being. Frequently, one wishes to superimpose such visual information upon the being's view of the real world. In other applications, it is desired to shield the user from a view of the environment, providing an exclusive view of the visual information.
Such displays include a number of components including, in a form known as a folded catadioptric display, an image generator, a beam splitter which receives the image light from the image generator, often via a series of lenses and other optic elements and sends a fraction, designated the reflected fraction, of such image light to a reflective combiner that is either non-transmissive or both allows light from the real world to pass through such combiner and reflects the image light such that both the real-world light and the image light are transmitted to the eye of the user through the beam splitter, often via another series of lenses or other optical elements. The beam splitter will transmit a fraction, designated the transmitted fraction, of the image light reflected from the collimator-combiner. In embodiments in which the combiner is at least partially transmissive, a fraction of the real-world light is also transmitted by the beam splitter.
Previous devices included a number of additional components. Some devices have included corrective optical elements. Other devices have included a depixelator, e.g., as described in PCT/US94/01390 filed Feb. 7, 1994 for "Depixelated Visual Display" (incorporated herein by reference). Still other devices have included apparatus for intensifying the visual display such as those described in PCT/US94/01391, filed Feb. 7, 1994 for "Intensified Visual Display" (incorporated herein by reference).
In designing a system for providing a generated image to the eye or eyes of a user, various factors are often in opposition. Although it is desirable to provide an image which has high quality so as to not only provide a pleasing and attractive display for the user but also to reduce eyestrain, very often the techniques used to produce such a pleasing image have been contrary to goals of an apparatus which is lightweight, low-cost, and relatively easy to design, fabricate and/or repair. Many previous devices have required expensive and heavy series of optical elements such as lenses to achieve a desired picture quality. Other devices have simply accepted a lower-quality image in order to achieve goals of low-cost or light weight. For example, some previous devices have failed to provide a flat focal field to the user. Others have resulted in a poor image contrast, particularly at high viewing angles of the image. Many devices have deprived the user of the full image in order to mask-off unwanted light near the edge of an image generator.
Accordingly, it would be useful to provide a personal, visual display apparatus which provides a high quality of image, which is low cost, lightweight, comfortable and has increased ease of design, fabrication, repair and the like.